Premier Motorsp

Vaughn--

I get them hot by driving the hell out of them. It is ok to slide. I don't baby them at all. Now a question for you: Why does my ABS suck so bad?

CC--

I have no doubt your car will get them hot enough. I'll bet an R3S04 would be dead in one session on your car.

NetManiac--

No inside info. I buy 'em from Tire Rack just like everyone else. The omission of the 245 and 275 17 inch sizes is strange.

Paul--

I can't see using a 265/285 combo without really under using the front tires. And since they need good heat to stick well, it probably would not increase the grip level. 265/315 would be great but probably impossible to fit under a narrow 993. The Michelin people are adamant about using wide wheels. They say that a 10 is narrow for the 285. The 265 would require a 9.5 which seems unlikely to fit under a narrow body.


Chris Cervelli
Premier Motorsports

NetManiac

Yeah, seems strange to me too. I keep thinking if I go from my current 235/275 combo to 225/255 it would be a wash. I'm getting stickier tire, but giving up a decent amount of contact patch. But maybe the extra stickiness is worth it.

Mark in Baltimore

Great thread, Chris.

1) How low are your starting out with your cold pressures and where do you end up with your hot pressures?

2) Also, what's the lowest pressure you'd safely ever use? I've been dropping my cold pressures down to 24 psi and have been really pushing the car to get the tires up to temp, but it seems that 165-175 degrees is about the hottest I can get the rears, my fronts being stuck in the 140-150 degree range.

993RSCS

Bill,

Yes it is Lee's previous RS. I am looking forward to getting it out on the track. I am coming from a 996TT so I figure there is going to be some learning curve.

Chris,

I believe that Lee ran 265/285 Cups but wasn't happy with them although they did fit. I have been very happy with the cups on my 996TT in stock sizing 225/295 with great wear and stick. The car has RSO3's on now that have multiple heat cycles but pretty good tread left. I will try to burn these up at No Problem raceway and then mount the MPSC's. I also have a set of the Dunlop R compound tires in 285/255. Do you have any experience with the Dunlops?

Paul

924RACR

Probably 'cause it's not good Bosch ABS!

Seriously, I'd expect it'd be weak on-track due to tire differences and suspension differences. But when you say it sucks, exactly how does it suck? In what circumstances/maneuvers? I've driven my ABS on track with Hoosiers (the '03's), and it held up well, but that was my tuning, Bosch 5.3 system, and it was still stock suspension... do you know what sort is in your car? We only deal with US-built cars over here, of course, Germany gets all the "fun" stuff...

Skip Wolfe

Has anyone heard if Michilen is going to expand their size offerings. The I would like to run 245/275-17, but the biggest they offer is a 255.

Premier Motorsp

Vaughn--

The car is a 1996 993 US model converted to RS specs. It still has the standard 3-channel ABS.

It looks like the ABS abitrarily will not allow decel beyond a certain point, regardless of wheel slippage. The ABS seems to be running almost all the time, even though I rarely feel the need for it.

The car is very stiff but the bump compliance is decent. I try to carry the braking WAY past turn in and the ABS does ok in this situation. I think the rear channel is what overreacts.

Does this make any sense?

Chris

924RACR

Yeah, pretty much... I'd suspect you'd be better off pulling the thing out and running a prop valve... Varied wheel/tire diameters from stock could be hurting you even worse, in fact, as I'm thinking about it... but 3-channel systems are pretty old, too, which doesn't help your cause (old software).

carreracup21

I ran the 245/275 S04's at this weekends CMP club race and won D class in my 964 USA cup (2800 lbs.). I had some very fast qualifying laps including a 1:46.574 which may be a D class record at that track ? That lap was in the 2nd cycle and was driven with very aggressive slip angle and trail braking rotation. Ambient outside temp. was @ 48 - 50. The S04's cannot be drivin like that for long before giving up and my race pace had to be much slower like 1:49 - 1:50's. I would like to have a tire that could be driven hard through the whole race without going away, but I also don't like the idea of a hard break away like you describe. I guess I may have to give them a try. Aside from the expense, I have grown fond of the hoosiers and have not had any premature cording as has been reported. I usually get 10 - 12 cycles out of them before they are done. My camber is nowhere near the levels you describe for the MPSC's. I run the S04's at 41-42 psi hot.

nman413

Has anyone run Toyos on a 993Turbo specifically a 245/305 combo?

Jack Kramer

Great thread Chris.

Your experiences mirror mine. I tried the S04's this year and was completely disappointed. I started the year with 2 sets of 18" 245/285 S04s, and a set of 225/265 MPSC's from the previous year.

I never got more than a day from the 285s on the rear. I'm an instructor so this includes both my runs as well as rides for my students, probably 6-8 heats cycles per day. Hoosier stepped up and replaced the 285s w/ 2 sets of 275s. The 275s lasted a longer, but they never lasted thru an entire 3 day event.

Meanwhile, the MPSC's kept chugging along - good until the very end. I'm glad I had them as my "backup". I ended up using them for at least a day each event.

My lap times on the Hoosiers were somewhat better than those on the MPSCs, but they were surprisingly close, given the MPSCs had a 20mm size disadvantage, and they were older with more heat cycles on them.

I found the Hoosiers and the MPSCs to have very different feels, much like you discribed. The car seemed to move around more on the S04's. This was disconcerting at first, as I was used to the MPSC's, which as you indicated, take a set and hold it consistently until they let go rather abrubtly. The car starts to move around much earlier with the Hoosiers, but it became quite a comfortable feeling once I realized it wasn't telegraphing immediate doom. I never really felt the S04's giving up the ghost during a session. I'm a DE guy so I don't stress the tire like a racer would. They corded before they showed any real degradation due to heat cycles

The MPSC's are very consistent thru their life with the exception of thier last few heat cycles when there just isn't enough rubber to dissapate heat. And as you said, their life span is multiple times that of the S04. I did find them to be slower than the S04's during the 1st couple of laps as they got up to temp.

For reference, I have PSS9's, RSR bars, and my 993's camber is -2.5 front, -2 rear. My starting MPSC pressure was 26-28, 32-36 hot. I tried a couple of pounds lower and found them to be very slick. I typically liked pressures a couple of pounds higher than what Michelin recommended. (These pound or two pressure variences we are discussing are probably within the error range of our pressure guages) Never took temps, but the tires work very evenly across the tire face both front and rear.

Hoosier is going to give me another set of 275s as they say they have corrected the cording problem. But, I'm still going to get another set of MPSCs and somehow I suspect I'll be using them next year

Premier Motorsp

Sounds like your experience is quite similar to mine. Don't be fooled by Hoosier though. Here is what is I have seen up til now:

285/30 18 on the rear. These cord the inside in 3 sessions if driven 100%. On your Turbo I'll bet I could cord them in one session. This tire is the worst case scenario since the air volume is so small. The stress is really high and the lifespan shows this.

All other sizes, including 17's. Guess what, they ALL cord prematurely. There is a very simple relationship between stress and lifespan. Faster drivers and heavier cars cord the tires faster. More negative camber (or dynamic positive camber) makes the situation worse. The outer edge is just as prone to cording as the inner.

I have not seen even one R3S04 wear out properly. They are pretty fast though. It makes me wonder how they would perform if they were designed properly.

Chris Cervelli
Premier Motorsports

carreracup21

Chris,
What kind of toe settings are you using on the rear ? I have gone through about 7 sets of the S04's in the 275/35/18 size on the rear and I have only seen cord on one set at about 12 cycles. I know of another racer who won races at Summit in cycles 7 and 10 without problems.

Larry Herman

I am about at my wits end concerning tires. I have run Pirelli slicks, and they either flat or go off during the weekend. I just ran a set of Dunlop SSRs at VIR, and although they are wearing fine, the rears just got progressively looser during the weekend. I guess that I will try the MPSCs next, but it really sucks to have to spend $1200 per DE. At least if I was club racing, the $30 trophy would justify the cost!

Jack Kramer

carreracup,

When did you start using the 275 S04s? Michelin has supposedly "fixed" them. Maybe you have the "new & improved" version.

BTW - They told me to stick with the 275s. They say the 285s do not have the appropriate load rating to handle the rear of a Porsche.